Convergence layers for network devices and method for transmitting data traffic

ABSTRACT

A network device for an ad-hoc established device network is described, which comprises a content detection layer for detecting the content type of external traffic received by said network device. According to the content type, the external traffic is routed to a content-specific convergence layer dedicated to handling the respective content type. Said content-specific convergence layers exchange network traffic with other network devices via content-specific connections that are suited to the requirements of the respective content type. On the part of a target network device, the received data stream can be routed to any external protocol. Thus, the device network allows interoperability between different external networking protocols.

The invention is related to a network device for use in an ad-hocestablished device network, to a device network, and to a method fortransmitting data traffic via a device network.

For a variety of home multimedia applications and business applications,it is important to establish networks, preferably wireless networks, forexchanging data and messages between different devices that are part ofthe network. In a typical business application scenario, a mobileterminal gets services over a fixed corporate or public infrastructure.In an exemplary home application scenario, a low-cost and flexiblenetworking is supported to interconnect wireless digital consumerdevices.

The ETSI Project BRAN (Broadband Radio Access Networks) has defined thestandard HiperLAN (High Performance Radio Local Area Network), whichprovides high-speed multimedia communications between differentbroadband core networks and mobile terminals. HiperLAN/2 provides aflexible platform for a variety of business and home applications thatcan support a set of bit rates up to 54 Mbit/s. The HiperLAN/2 standardis an example how data can be transmitted between different devices in awireless network. The invention is not limited to wireless networksaccording to the HiperLAN/2 standard, though. The invention is notlimited to wireless networks. It can also be applied in wired networks.

A typical device network comprises several devices, with one of thedevices acting as a controller that controls the other devices that actas mobile terminals. When different devices are brought within reach ofeach other, they start exchanging messages and establish a so-calledad-hoc network, with one of the devices assuming the controlfunctionality.

In section 6.2 of ETS1 BRAN HiperLAN2 Standard Spec: DLC home extension(ETSI TS 101 761-4V1.3.2 (2002-01), it is described how multipleconvergence layers supporting different external networking standardscan be active simultaneously within one wireless local area network.

It is an object of the invention to provide a network device and amethod for routing data traffic of an external networking protocolthrough a local area network, whereby interoperability between differentexternal networking technologies is supported.

The object of the invention is solved by a network device according toclaim 1, by a device network according to claim 13, and by a method fortransmitting data traffic via a device network according to claim 21. Acomputer program product according to the present invention is definedin claim 24 and a computer readable storage medium is defined in claim25.

According to the invention, the network device for a device networkcomprises a content detection layer for detecting the content type ofexternal traffic received by said network device. In dependence of thedetected content type, said external traffic is passed to acontent-specific convergence layer that is dedicated to handling therespective content type. Furthermore, the network device comprises a setof content-specific convergence layers, which exchange network trafficwith other network devices of said device network via content-specificconnections. Said content-specific connections are suited to therequirements of the respective content type.

In prior art solutions, external traffic received by a network devicehas been passed, according to the protocol of said external traffic, toa protocol-specific convergence layer. For example, IEEE 1394 datatraffic has always been handled by a IEEE 1394-specific convergencelayer, and Ethernet traffic has been handled by an Ethernet-specificconvergence layer. The respective convergence layer has been responsiblefor transmitting the external traffic to its respective target networkdevice, whereby the connection for transmitting the external trafficwithin the device network has been set up according to said externalnetwork.

According to the invention, when external traffic is received by anetwork device, the content type of said external traffic is detected bya content detection layer. For example, it might be detected that theexternal traffic is “packet-based data traffic”. Alternatively, saidexternal traffic might be “real-time critical data traffic”, for examplean audio or video data stream. When the content type has been detected,the received data traffic is passed to a convergence layer that isspecific for said type of content. Thus, instead of protocol-specificconvergence layers, content-specific convergence layers are used forsetting up and releasing connections to other network devices within thenetwork, and for transmitting data traffic within the device network.The content specific connections that are built up by thecontent-specific convergence layers are suited to the requirements ofthe respective content type.

The invention is based on the fact that the requirements for a datatransmission within a device network do not depend on the protocol ofthe external traffic in the first place. It is possible to transmitpacket-based data traffic via a IEEE 1394 interface (IPover1394), thoughthe standard IEEE 1394 is mostly used for the transmission of video datastreams. Vice versa, it is also possible to transmit real-time criticaldata via an IP network, which is typically used for packet-based datatransmission. The requirements for a data transmission within the devicenetwork depend in the first place on the content type of the externaltraffic. The requirements imposed by the content type define theparameters of the data connection that is established between the sourcenetwork device and the target network device. For example, a real-timecritical video data stream requires that the transmission delay neverexceeds a predefined threshold, and that a fixed bandwidth ispermanently available for said data transmission. Generally, there areno such restrictive requirements for packet-based data transmission.

According to the invention, for each content type, a specificconvergence layer is provided, which handles data streams of saidcontent type according to the content-specific requirements. Thecontent-specific convergence layers are responsible for establishing andreleasing content-specific connections within the device network, andfor transmitting the respective external data traffic within the devicenetwork.

Within the network, the external traffic is transmitted from the sourcenetwork device, which has received said traffic from an externalnetwork, to a target network device. On the part of the target networkdevice, the arriving data stream is taken care of by a correspondingconvergence layer that is responsible for the respective content type.To said target network device, any external network may be connected.The convergence layer on part of the target network device doesn't haveto route the traffic to the external protocol said traffic has emanatedfrom. Instead, the received data traffic may be mapped to any externalprotocol that is able to accept the respective content type. Forexample, a video data stream emanating from a IEEE 1394 interface can bemapped, after it has been transmitted within the device network, to aIEEE 1394 interface again. Alternatively, the video data stream can alsobe mapped, on part of the target network device, to an IP interface.This kind of data exchange between different external networkingtechnologies has not been possible in the prior art. The inventiveconcept of content-specific convergence layers allows for aninteroperability between different external networking standards. Incase two completely different external network protocols can handle thesame content type, it is possible to receive external traffic of a firstexternal protocol, route said traffic through the device network,whereby an internal protocol is used, and map the traffic, on the partof the receiving network device, to a second external protocol. Thedevice network can be seen as an adapting means for adapting a firstkind of external traffic to a second kind of external traffic.

One advantage of the inventive solution is that the available bandwidthof the device network is used more effectively by allowing access todifferent traffic types. Another advantage is that new networkingtechnologies and traffic types can be integrated easily into theexisting convergence layer architecture. Due to the generic design ofthe relevant modules, large amounts of existing code can be reused inthe process of the integration.

Preferably, one of said content types is real-time critical data,whereby said set of content-specific convergence layers comprises aconvergence layer dedicated to handling real-time critical data. Whenreal-time critical data, for example an audio or video data stream; istransmitted from a first network device to another network device of thedevice network, the following requirements have to be fulfilled: Firstof all, transmission delays that exceed a certain amount are notacceptable. Furthermore, for the transmission of a real-time criticaldata stream, a certain bandwidth has to be permanently available inorder to allow for a continuous transmission of said data stream. Aconvergence layer dedicated to handling real-time critical data can setup content-specific connections within the device network that allow tofulfil the above-mentioned requirements.

Further preferably, one of said content types is packet-based data,whereby said set of content-specific convergence layers comprises aconvergence layer dedicated to handling packet-based data. When regularpacket-based data traffic has to be transmitted within the devicenetwork, there are no specific requirements concerning the transmissiondelay and available bandwidth as there are in case of real-time criticaldata. A convergence layer dedicated to handling packet-based data willtherefore set up a content-specific connection for the transmission ofsaid data, whereby the available network resources are used in a moreflexible way. In particular, it is not necessary to reserve a predefinedbandwidth for the transmission of said packet-based data.

According to a preferred embodiment of the invention, said externaltraffic is at least one of Ethernet traffic, IEEE 1394 traffic, UMTStraffic or PPP traffic. The Ethernet protocol is the major protocol foraccessing the internet. IEEE 1394 is the most common standard for dataexchange between audio and video devices and allows for largetransmission bit rates. UMTS is an example for a third generation mobilecommunications protocol, and PPP (point-to-point protocol) permits toestablish point-to-point connections between two devices. Thus, thenetwork device can be connected to a large range of current networkingtechnologies simultaneously.

Preferably, said network device comprises hardware connectivity for atleast one of Ethernet traffic, IEEE 1394 traffic, UMTS traffic or PPPtraffic. Data packets received via said hardware connections areconverted into the internal network protocol of the device network. Viceversa, data packets of the internal network protocol received from othernetwork devices are converted into data packets of the externalnetworking technology. Then, these data packets are sent to the externalnetwork via said hardware connection.

Preferably, said network device is an access point of said devicenetwork. The task of an access point is to provide access to differentexternal networking technologies and networking services, for example tothe internet. Therefore, the access points should be equipped withmultiple content-specific convergence layers in the first place, becausesaid access points have to handle different kinds of data trafficreceived from various external networks.

According to a preferred embodiment of the invention, said contentdetection layer analyses if said Ethernet traffic is real-time criticaltraffic, e.g. in connection with RTP, RTCP, RSVP, or RTSP traffic,whereby in case said Ethernet traffic is real-time critical, it ispassed to a convergence layer dedicated to handling real-time criticaldata. Each data packet of Ethernet data traffic comprises type fieldinformation indicating the content of the respective Ethernet datapacket. Thus, the content detection layer can easily determine if saidEthernet traffic Is real-time critical or not. If the result ofanalysing the type field information is that said Ethernet traffic isreal-time critical, it is passed to the convergence layer that handlesreal-time critical data. Therefore, in the case of Ethernet packets, thedetection of the respective content type can be implemented in a verysimple way.

Further preferably, said content detection layer analyses if saidEthernet traffic is not real-time critical traffic, i.e. of some otherprotocol type and thus packet-based traffic, whereby in case saidEthernet traffic is not real-time critical, it is passed to aconvergence layer dedicated to handling packet-based data. The typefield information of an Ethernet packet indicates the content of saiddata packet. The content detection layer can easily detect whether thereceived Ethernet traffic is packet-based data traffic or not.Packet-based data traffic is passed to a convergence layer dedicated tohandling this content type.

Preferably, said content detection layer analyses if said IEEE 1394traffic is packet-based data traffic, whereby in case said IEEE 1394traffic is packet-based data traffic, it is passed to a convergencelayer dedicated to handling packet-based data. Further preferably, saidcontent detection layer analyses if said IEEE 1394 traffic is real-timecritical data traffic, whereby in case said IEEE 1394 traffic isreal-time critical data traffic, it is passed to a convergence layerdedicated to handling real-time critical data. Via a IEEE 1394interface, either real-time critical IEEE 1394 data traffic orpacket-based data traffic (IPover1394) can be transmitted. Also withregard to 1394 traffic, it is possible to analyse at low expense therespective content type. According to the content type, the IEEE 1394traffic is either passed to a convergence layer for handling real-timecritical data, or to a convergence layer for handling packet-based datatraffic.

According to a preferred embodiment of the invention, saidcontent-specific convergence layers comprise a common part, whichsegments data packets of said external traffic into a multitude ofcorresponding data packets of said device network's internal protocol,and which reassembles data pakkets of said device network's internalprotocol into corresponding data pakkets of the respective externaltraffic. All the external networking technologies mentioned so far haveone thing in common: They use variable size data packets which comprisemore bytes than the rather small LCH (Long Transport Channel) datapackets used within the HiperLAN/2 network, which only comprise 48bytes. Therefore, data packets of the external protocol have to besegmented into a multitude of HiperLAN/2 data packets.

Data packets received from the HiperLAN/2 network have to be reassembledinto the data packets of the respective external protocol. Instead ofproviding each one of the convergence layers with a unit for segmentingand reassembling data packets, this task is accomplished, for all theconvergence layers, by the common part of the convergence layers. Thecommon part segments data packets arriving from the respective externalnetwork into a multitude of data packets of the internal network'sprotocol, and reassembles data packets of the internal protocol intovariable size data packets of the respective external protocol. Byimplementing said common part, the structure of the content-specificconvergence layers can be simplified. Another advantage is that in casea new convergence layer for another content type is to be implemented,programming said new convergence layer is simplified, because thefunctionality of the common part can be used.

Preferably, said content-specific convergence layers are operable to beused simultaneously within the same device network. Therefore, a networkdevice can simultaneously handle data streams of different content type.

According to the invention, a device network is set up, which comprisesat least one network device with a content detection layer, and with aset of content-specific convergence layers as described above.

Preferably, content-specific connections are set up and released betweenthe network devices of said device network, whereby a content-specificconnection is set up between a content-specific convergence layer of afirst network device which supports a certain content type, and arespective content-specific convergence layer of a second network devicewhich supports the same content type. Between convergence layerssupporting the same content type, a connection can be established. Assoon as the connection is established, any amount of data packets can betransmitted between the two content-specific convergence layers. Bydefining content-specific connections for handling data transmissionswithin the ad-hoc established device network, it is possible to definethe parameters of the data transmission according to the content type,and to choose these parameters according to the desired bandwidth, errorhandling, etc.

According to a preferred embodiment of the invention, the externaltraffic exchanged with said content-specific convergence layer of saidfirst network device may be of a different kind than the externaltraffic exchanged with said content-specific convergence layer of saidsecond network device. On the part of the target network device, thereceived data stream may be forwarded to any external protocol that iswilling and able to accept the respective content type. The data streamthat has been transmitted via the ad-hoc established device network canthus be distributed to an external network that is different from theexternal network the data stream has emanated from. Data traffic from afirst external networking technology may be routed to a second externalnetworking technology. The device network serves as an adapting meansfor all kinds of network traffic. This makes the device network,preferably the wireless LAN technology, much more powerful and flexible.

Preferably, in case said content-specific connection is for a contenttype which requires a quality of service feature, a fixed bandwidth isreserved for said content-specific connection. The “quality of service”feature is a well-known feature for the transmission of video data. Acertain bandwidth is reserved for the transmission of the video datastream, and thus, a certain quality of service (QoS) is guaranteed. Whentransmitting video data streams or any other data traffic supporting thequality of service feature via a device network, it is possible to setup the connection in a way that the quality of service feature issupported.

Further preferably, for each content-specific connection, the contenttype supported by said content-specific connection is registered. Anytraffic transmitted via the content-specific connection can be passed,on the part of the target network device, to the correspondingcontent-specific convergence layer dedicated to handling the respectivecontent type.

Further preferably, said device network is a wireless local area network(WLAN), and in particular a HiperLAN/2 network. HiperLAN/2 is a Europeanstandard for wireless local area networks.

According to a preferred embodiment of the invention, the exchange ofcontrol messages and data packets between different network devices ofsaid device network is effected according to a TDMA transmission scheme.Preferably, a set of time slots of said TDMA transmission scheme may bereserved for a certain content-specific connection. By doing this, apredefined transmission capacity can be assigned to a certainconnection. This is one way of realizing the above-mentioned quality ofservice feature.

Further features and advantages of preferred embodiments according tothe present invention will be explained below in conjunction with theaccompanying drawings, in which

FIG. 1 shows how different networking technologies interact In order toprovide a networking environment;

FIG. 2 shows a wireless local area network comprising two networkdevices according to the prior art;

FIG. 3 shows a wireless local area network, whereby both real-timecritical and regular packet-based data streams are transmitted via thewireless LAN;

FIG. 4 depicts the structure of the protocol stack for the HiperLAN/2standard; and

FIG. 5 shows how higher layer packets, for example Ethernet packets, aremapped onto layers of the HiperLAN/2 standard.

FIG. 1 shows the interplay of different network protocols in anetworking environment. The Internet 1 provides the backbone for allkinds of data exchange services. In an office environment 2, servers 3and access points 4 for wireless data transmission are connected bymeans of the Ethernet protocol. In order to establish wireless localarea networks for connecting mobile terminals 5 to said access points 4,the Ethernet protocol can be converted into a suitable protocol forwireless data transmission, e.g. into the HiperLAN/2 protocol. Also in ahome environment 6, the HiperLAN/2 protocol is used for establishing anad-hoc device network for exchanging data between audio and videodevices 7, personal computers 8, organizers 9, etc. In the field ofmobile communication 10, the standards GPRS and UMTS are used forexchanging data packets between mobile devices 11 and base stations 12,and for accessing the Internet 1. For small distances, the Bluetoothprotocol is used. For all these applications, the Internet ServiceProvider 13 provides a high-bandwidth backbone 14 and all kinds of dataexchange services (email, world wide web. WAP, FTP, etc.).

In FIG. 2, a wireless local area network of the prior art is shown. Thewireless local area network comprises an access point 15, which acts asa central controller for the network, and a mobile terminal 16. Themobile terminal 16 exchanges data packets with the access point 15 viathe HiperLAN/2 protocol. The access point 15 comprises hardwareconnectivity for an external network protocol, the Network Type 1 (18),e.g. for the Ethernet. Furthermore, the access point 15 comprises aNetwork Type 1 convergence layer 17 for converting data packets receivedvia the Network Type 1 (18) into the HiperLAN/2 standard (19), and forconverting data packets received via the HiperLAN/2 (19) into theNetwork Type 1 standard (18).

In FIG. 3, a device network comprising four network devices withcontent-specific convergence layers are shown. An Ethernet device 20,which is connected to the Ethernet via IP (Internet Protocol), Is partof the device network 21. Preferably, the device network is a wirelesslocal area network (LAN), in particular according to the HiperLAN/2standard. The Ethernet device 20 can receive regular IP traffic 22 fromthe Internet. Regular packet-based IP traffic is transmitted accordingto protocols aside from those that are explicitly used for real-timecritical data (e.g. RTP, RTCP, RSVP, or RTSP). The Ethernet device 20can also receive real-time critical data traffic 23 via the Ethernetinterface, e.g. a video data stream. For the transmission of real-timecritical data traffic via an IP network, currently the protocols RTP(Real-Time Protocol), RTCP (Real-Time Control Protocol), RSVP (resourceReSerVation Protocol), and RTSP (Real-Time Streaming Protocol) are used.

Let us assume that real-time critical video data stream 23 emanatingfrom the Ethernet device 20 shall be transmitted via the device network21 to other network devices. The video data stream 23 is first passed toa content detection and routing layer 24, and said content detection androuting layer 24 detects that the arriving data stream utilizes one ofthe real-time critical protocol types. Therefore, the content type isidentified as “real-time critical data traffic”. Accordingly, thereal-time critical data stream is forwarded to a convergence layer 25dedicated to handling “real-time critical data traffic”. Besides theconvergence layer 25, other content-specific convergence layers exist,e.g. the convergence layer 26, which is dedicated to handling“packet-based data traffic”.

The content-specific convergence layer 25 establishes a content-specificconnection with a corresponding convergence layer on the part of thetarget network device. In case real-time critical data traffic has to betransmitted, the convergence layer 25 reserves a certain predefinedbandwidth when establishing the connection to the respective targetnetwork devices. Then, the IP data packets of the real-time criticaldata traffic are segmented into a set of corresponding data packets ofthe internal protocol of the device network 21. This task can be carriedout by a separate module which is a common part of the content-specificconvergence layers 25 and 26. In case the device network 21 is aHiperLAN/2 network, 48 byte packets of the type LCH (Long TransportChannel) are used within the device network 21.

Now, the video data stream 23 of our example is transmitted via thedevice network 21 to the respective target network devices. There, thearriving data packets are forwarded to a content detection and routinglayer 27. In case a target network device, e.g. a IEEE 1394 device 28 oran Ethernet device 29, has indicated that it is willing to accept arespective traffic type, the content detection and routing layer 27forwards the received data stream to the respective target device. Incase the Ethernet device 29 has indicated that it is willing to acceptthe video data stream, the received video data stream is routed (30) tothe Ethernet device 29. There, the short LCH data packets arereassembled to build IP packets, and the real-time critical video datastream is again converted into an appropriate protocol for real-timecritical data. The video data stream can then be forwarded to the IPnetwork to which the Ethernet device 29 is connected.

So far, it has been described how the video data stream 23, which is anIP data stream, is converted to the device network's internal protocoland transmitted via said device network to another Ethernet device 29.The video data stream 23, which has emanated from an IP network, doesn'thave to be routed to an Ethernet device, though. The content detectionand routing layer 27 can also route the received real-time critical datastream to the IEEE 1394 device 28 when the IEEE 1394 device 28 requestsit. On part of the IEEE 1394 device 28, the LCH data packets of theinternal protocol are reassembled into a video data stream 31 accordingto the IEEE 1394 protocol. The real-time critical video data stream canthen be forwarded to the IEEE 1394 network to which the IEEE 1394 device28 is connected. The inventive concept of content-specific convergencelayers and content-specific routing allows to transform a real-timecritical IP data stream into an IEEE 1394 data stream. Besides that, itis also possible to transmit the real-time critical video data stream 23emanating from the Ethernet to both an Ethernet device 29 and a IEEE1394 device 28.

In the following, a second example will be discussed. On the part of theEthernet device 20, regular IP traffic 22 is received from the Internet.The regular IP traffic is passed to the content detection and routinglayer 24, which detects that the content type is “packet-based datatraffic”, which is not real-time critical. The regular IP traffic 22 isthen passed to the convergence layer 26, which Is dedicated to handling“packet-based data traffic”. The IP packets are segmented into the LCHdata packets used within the HiperLAN/2 network. A connection is set upwithin the device network 21, and the data traffic is transmitted to thecontent detection and routing layer 27. From there, the traffic can berouted to the Ethernet device 29. The received packets of the internalprotocol are reassembled into IP packets, and the IP data stream 32 isobtained.

Alternatively or additionally, the data traffic can be routed from thecontent detection and routing layer 27 to the IEEE 1394 device 28.There, the received packets of the internal protocol are reassembledinto data packets according to the IEEE 1394 standard. Though the IEEE1394 standard is intended for the transmission of audio and video datastreams in the first place, it is also possible to transmit IP datapackets via an IEEE 1394 interface.

This is called “IPover1394”. Such an “IPover1394” data stream 33 isobtained on the part of the IEEE 1394 device 28.

Both real-time critical data streams and regular packet-based datatraffic can also emanate from a IEEE 1394 device 34 that is connected toan external IEEE 1394 network. The video data stream 35 can betransmitted from the IEEE 1394 device 34 via the convergence layer 25and the device network 21 to the IEEE 1394 device 28, or to the Ethernetdevice 29, or to both said devices. The IPover1394 data traffic 36 ispassed to the convergence layer 26, which handles packet-based datatraffic. Via the device network 21, the data traffic is routed to theIEEE 1394 device 28, or to the Ethernet device 29, or to both saiddevices.

In FIG. 4, the so-called protocol stack for the HiperLAN/2 standard isshown. The bottom layer is the Physical Layer 37, which deals with themodulation type and the actual data transmission. The next layer is theMedium Access Control (MAC) 38, which is part of the Data Link ControlLayer (DLC) 39. The MAC 38 schedules the data for transmission. A TDMA(Time Division Multiple Access) frame with time slots of 2 ms is used,and the MAC 38 assigns time slots of the TDMA frame to the variousconnections within the HiperLAN/2 network. The TDMA frame generated bythe MAC 38 is the typical transmission standard in the HiperLAN/2protocol. The Data Link Control Layer 39 further comprises an ErrorControl functionality 40.

Furthermore, the Data Link Control Layer 39 comprises a Radio LinkControl Sublayer (RLC) 41.

The highest layers of the HiperLAN/2 standard are the convergence layers42, which comprise a content type detection and routing layer 43, a setof content-specific convergence layers 44, 45, and a common part 46 ofsaid convergence layers. The content type detection and routing layer 43detects the content type of arriving data traffic and passes saidtraffic to a corresponding content-specific convergence layer. Theconvergence layer 44 handles packet-based data traffic, whereby theconvergence layer 45 handles real-time critical data traffic.

The common part 46 segments the variable size data packets of therespective external protocol into a multitude of data packets accordingto the HiperLAN/2 standard. Besides that, the common part 46 convertsHiperLAN/2 packets into data packets of an external protocol byreassembling the HiperLAN/2 packets.

The respective hardware connectivity is addressed by means of drivers47, 48, 49. The convergence layer 47 is responsible for handling the PPP(point-to-point) protocol, which is an external protocol used forpoint-to-point connections. The driver 48 supports the IEEE 1394protocol, and the driver 49 supports the Ethernet protocol.

In FIG. 5, it is shown how higher layer packets, for example Ethernetpackets, are mapped onto layers of the HiperLAN/2 standard. Again, thePhysical Layer PHY is the bottom layer, and a PHY burst 52 comprisingseveral Long Transport CHannel Packets (LCH) is shown. At the Data LinkControl Layer (DLC), a Long Transport CHannel Packet (LCH) 53 is dividedinto a header 54, a DLC SDU 55, and a Cyclic Redundancy Check (CRC) 56.At the Convergence Layer (CL), the DLC SDU 55 is divided into 12 bits offlags (57) and 384 bits or 48 bytes of Payload (58). A higher layerpacket, e.g. an Ethernet packet 59, is segmented into a multitude ofthese 48 bytes packets 58, 60, which are transmitted as LCH packetsaccording to the HiperLAN/2 standard.

1. Network device for a device network characterized by a contentdetection layer (24, 43) for detecting the content type of externaltraffic received by said network device, and for passing said externaltraffic, in dependence of the detected content type, to acontent-specific convergence layer (25, 26, 44, 45) dedicated tohandling the respective content type, and a set of content-specificconvergence layers (25, 26, 44, 45), which exchange network traffic withother network devices (28, 29) of said device network (21) viacontent-specific connections, whereby said content-specific connectionsare suited to the requirements of the respective content type. 2.Network device according to claim 1, characterized in that one of saidcontent types is real-time critical data, whereby said set ofcontent-specific convergence layers comprises a convergence layerdedicated to handling real-time critical data.
 3. Network deviceaccording to claim 1, characterized in that one of said content types ispacket-based data, whereby said set of content-specific convergencelayers comprises a convergence layer dedicated to handling packet-baseddata.
 4. Network device according to anyone of the preceding claimsclaim 1 characterized in that said external traffic being at least oneof Ethernet traffic, IEEE 1394 traffic, UMTS traffic or PPP traffic. 5.Network device according to claim 1, characterized in that said networkdevice comprises hardware connectivity for at least one of one ofEthernet traffic, IEEE 1394 traffic, UMTS traffic or PPP traffic. 6.Network device according to claim 1, characterized in that said networkdevice is an access point of said device network.
 7. Network deviceaccording to claim 1, characterized in that said content detection layeranalyses if said Ethernet traffic is real-time critical traffic, wherebyin case said Ethernet traffic is real-time critical, it is passed to aconvergence layer dedicated to handling real-time critical data. 8.Network device according to claim 1, characterized in that said contentdetection layer analyses if said Ethernet traffic is not real-timecritical traffic, whereby in case said Ethernet traffic is not real-timecritical, it is passed to a convergence layer dedicated to handlingpacket-based data.
 9. Network device according to claim 1, characterizedin that said content detection layer analyses if said IEEE 1394 trafficis packet-based data traffic, whereby in case said IEEE 1394 traffic ispacket-based data traffic, it is passed to a convergence layer dedicatedto handling packet-based data.
 10. Network device according to claim 1,characterized in that said content detection layer analyses if said IEEE1394 traffic is real-time critical data traffic, whereby in case saidIEEE 1394 traffic is real-time critical data traffic, it is passed to aconvergence layer dedicated to handling real-time critical data. 11.Network device according to claim 1, characterized in that saidcontent-specific convergence layers comprise a common part, whichsegments data packets of said external traffic into a multitude ofcorresponding data packets of said device network's internal protocol,and which reassembles data packets of said device network's internalprotocol into corresponding data packets of the respective externaltraffic.
 12. Network device according to claim 1, characterized in thatsaid content-specific convergence layers are operable to be usedsimultaneously within the same device network.
 13. Device network,comprising at least one network device according to claim
 1. 14. Devicenetwork according to claim 13, characterized in that content-specificconnections are set up and released between the network devices of saiddevice network, whereby a content-specific connection is set up betweena content-specific convergence layer of a first network device whichsupports a certain content type, and a respective content-specificconvergence layer of a second network device which supports the samecontent type.
 15. Device network according to claim 13, characterized inthat the external traffic exchanged with said content-specificconvergence layer of said first network device may be of a differentkind than the external traffic exchanged with said content-specificconvergence layer of said second network device.
 16. Device networkaccording to claim 13, characterized in that in case saidcontent-specific connection is for a content type which requires aquality of service feature, a fixed bandwidth is reserved for saidcontent-specific connection.
 17. Device network according to claim 13,characterized in that for each content-specific connection, the contenttype supported by said content-specific connection is registered. 18.Device network according to claim 13, characterized in that said devicenetwork is a wireless local area network (WLAN), and in particular aHiperLAN/2 network.
 19. Device network according to claim 13,characterized in that the exchange of control messages and data packetsbetween different network devices of said device network is effectedaccording to a TDMA transmission scheme.
 20. Device network according toclaim 19, characterized in that a set of time slots of said TDMAtransmission scheme may be reserved for a certain content-specificconnection.
 21. Method for transmitting data traffic via a devicenetwork, characterized by the follow steps: detecting a content type ofexternal traffic arriving at the device network, passing said externaltraffic, in dependence of the detected content type, to acontent-specific convergence layer (25, 26, 44, 45) dedicated tohandling the respective content type, and transmitting network trafficto other network devices (28, 29) via content-specific connections,whereby said content-specific connections are suited to the requirementsof the respective content type.
 22. Method according to claim 21,characterized in that content-specific connections are set up betweentwo network devices before transmitting said network traffic betweensaid two network devices in accordance with said content type. 23.Method according to claim 21, characterized in that after the networktraffic between said two network devices has been transmitted inaccordance with said content type, said content-specific connectionbetween said two network devices is released.
 24. Computer programproduct comprising computer program means adapted to perform the methodsteps as defined in claim 21 when being executed on a computer, adigital signal processor or the like.
 25. Computer readable storagemeans, storing thereon a computer program product according to claim 24.